The present invention relates to a method for treating bisphenol A tar at an elevated temperature with an alkylated phenol, such as cresol, in the presence of an acid catalyst to form phenol and a polyalkylated xanthene. The polyalkylated xanthene can be recovered and used as a heat transfer fluid, or in particular instances, can be readily converted to a polyester intermediate, such as a xanthene dicarboxylic acid, dicarboxylic acid halide, or ester thereof.
As shown by Carnahan, U.S. Pat. No. 4,277,628, a bisphenol A waste stream, resulting from the reaction of phenol and acetone in the presence of an acidic condensing agent, can be treated with aluminum isopropoxide to obtain good yields of phenol. Additional methods for recovering phenol and bisphenol A values from bisphenol A waste streams are shown by Kiedik et al, U.S. Pat. No. 4,131,749 and Mitchell, U.S. Pat. No. 4,180,683. Although a number of procedures are available for salvaging bisphenol values from bisphenol A waste streams, or bisphenol A tar, additional methods are constantly being evaluated. The expression "bisphenol A tar" or "bisphenol A waste stream" as used hereinafter, means semi-volatile, or non-volatile organic waste, produced as a by-product in the manufacture of bisphenol A consisting essentially of the following organic compounds:
bisphenol A (5-95% by weight) PA1 o,p-bisphenol A (0-95% by weight) PA1 bisphenol-indan (0-50% by weight) PA1 4-(4-hydroxyphenyl)-2,2,4-trimethylchroman (0-50% by weight) PA1 2-(4-hydroxyphenyl)-2, 4,4-trimethylchroman (0-50% by weight) PA1 trisphenol A (0-95% by weight); PA1 other products containing acetone and phenol residues arising from acid treatment of phenol and acetone (0-80%). PA1 (a) forming a mixture at a temperature of from about 90.degree. C. to 200.degree. C. which comprises by weight, from about 1 part to about 50 parts of bisphenol A tar, per 100 parts by weight of a C.sub.(1-4) alkyl phenol selected from the group consisting of a meta substituted C.sub.(1-4) alkyl phenol, a para substituted C.sub.(1-4) alkylphenol, a mixture thereof, and a 3,4-di C.sub.(1-4) alkyl substituted phenol, in the presence of an effective amount of an acid catalyst, PA1 (b) distilling from the resulting mixture of (a), a phenolic material consisting essentially of a member selected from the group consisting of a mixture of phenol and a C.sub.(1-4) alkyl phenol, a mixture of phenol and a 3,4 di-C.sub.(1-4) alkyl phenol, a C.sub.(1-4) alkyl phenol,and a 3,4 di-C.sub.(1-4) alkyl phenol, and, PA1 (c) recovering phenol from the distillate and a polyalkylated xanthene of formula (1) from the residue of (b). PA1 (d) forming a mixture at a temperature of from about 90.degree. C. to about 200.degree. C., which comprises by weight, from about 1 part to about 50 parts of a bisphenol A containing material, per 100 parts by weight of an alkyl substituted phenol selected from the group consisting of a meta substituted C.sub.(1-4) alkyl phenol, a para substituted C.sub.(1-4) alkyl phenol, or a mixture thereof, in the presence of an effective amount of an acid catalyst, PA1 (e) distilling from the resulting mixture of (d), a phenolic material consisting essentially of a member selected from the group consisting of a mixture of phenol and the C.sub.(1-4) alkyl phenol,and the C.sub.(1-4) alkyl phenol, and PA1 (f) recovering a 9,9-dimethylxanthene from the residue of (e), substituted with two C.sub.(1-4) alkyl radicals which can be the same or different and located in the 3,6 position, the 2,7 position, or a mixture thereof, and PA1 (g) oxidizing the xanthene of (f) to form a xanthene dicarboxylic acid, or mixture thereof. PA1 9, 9-dimethylxanthene-3,6-dicarboxylic acid, PA1 9, 9-dimethylxanthene-2,7-dicarboxylic acid, PA1 9, 9-dimethylxanthene-2,6-dicarboxylic acid